1. Field of the Invention
The present invention relates to a silent chain in which a guide row made up of a pair of left and right guide plates and a middle plate and a non-guide row made up of a plurality of inner plates are alternately connected in a chain longitudinal direction by a pair of locker pins.
2. Description of the Related Art
Conventionally, as shown in FIGS. 4 to 7, a silent chain 500 is known in which a guide row 501 made up of a pair of left and right guide plates 510 and a middle plate 520 and a non-guide row 503 made up of a plurality of inner plates 530 are alternately connected in a chain longitudinal direction by a pair of locker pins 504 made up of a long pin 540 and a short pin 550.
The long pin 540 is fitted and fixed to a pin hole 511 of the guide plate 510 and is seated on a pin seat portion 522 of a pin hole 521 of the middle plate 520, and does not rotate relatively.
The short pin 550 is seated on a pin seat portion 532 of a pin hole 531 of the inner plates 530 and does not rotate relatively.
Accordingly, when a rolling surface 541 of the long pin 540 and a rolling surface 551 of the short pin 550 come into direct contact with each other and roll, the guide row 501 and the non-guide row 503 bend.
When the silent chain 500 is in a straight state, as shown in FIG. 5, the rolling surface 541 of the long pin 540 and the rolling surface 551 of the short pin 550 come into contact with each other at a contact point T1 on a pitch line P and can roll both upward and downward as indicated by the arrows.
When the silent chain 500 is wound around a sprocket and bends toward an inner peripheral side (hereinafter, referred to as “forward bending”), as shown in FIG. 6, the rolling surface 541 of the long pin 540 and the rolling surface 551 of the short pin 550 roll so that a contact point T2 is displaced toward an outer peripheral side (upward).
When the silent chain 500 bends toward an outer peripheral side (hereinafter, referred to as “backward bending”), as shown in FIG. 7, the rolling surface 541 of the long pin 540 and the rolling surface 551 of the short pin 550 roll so that a contact point T3 is displaced toward an inner peripheral side (downward).
The pin hole 521 and the pin hole 531 are respectively formed in a circular shape with the exception of the pin seat portions 522 and 533. The pin hole 521 of the middle plate 520 does not restrict relative movement of the short pin 550 in any way during bending, and the pin hole 531 of the inner plates 530 does not restrict relative movement of the long pin 540 in any way during bending.
Therefore, during both forward bending and backward bending, the silent chain 500 can bend freely within a rollable range of the rolling surface 541 of the long pin 540 and the rolling surface 551 of the short pin 550.
As a result, a restricting member such as a chain guide or a tensioner must be provided in order to restrict bending of the silent chain 500 and suppress vibration and undulation in a free span during use.
Since such restricting members come into direct contact with the silent chain, there is a risk of the restricting members becoming a new source of sliding resistance and contact noise.
In order to solve the problem described above, a known technique restricts bending with a silent chain's own structure by applying bending resistance using an elastic deformation of a locker pin (refer to Japanese Patent Application Laid-open No. 2013-210035).
Another known technique suppresses vibration and undulation of a silent chain by providing bending restricting portions (a straight bending displacement allowing surface 46 and a straight reverse warping preventing surface 48) above and below a pin hole (refer to Japanese Patent Application Laid-open No. 2001-173732).